(a) Technical Field
The present invention relates to a structure of a diplexer that prevents outputs of both signals from influencing each other by removing mutual interference between both signals when a signal having a high pulse frequency and a signal having a low pulse frequency are combined and radiated by using the same antenna, and more particularly, to a 2-channel diplexer structure with two channels in which a substrate having a predetermined size is configured, five microstrip lines are arranged on the top of the substrate to be parallel to each other with a predetermined interval wherein a front end of a first microstrip line and a front end of a third microstrip line are connected through a first connection line and a rear end of the third microstrip line and a rear end of a fifth microstrip line are connected through a second connection line to configure one microstrip line of  shape; a second microstrip line as an individual line is configured between the first microstrip line and the third microstrip line by the first connection line opened to a rear side by the first connection line; a fourth microstrip line as an individual line is configured between the third microstrip line and the fifth microstrip line opened to a front side by the second connection line, including a first port connected with the first connection line; a third port connected to a rear end of the second microstrip line; a fourth port connected with the second connection line; and a third port connected to a front end of the fourth microstrip line.
(b) Background Art
In general, a diplexer uses an LPF and an HPF instead of a BPF unlike a duplexer.
For example, as the diplexer used in the related art, four types (band splitters, wide bandpass diplexer & triplexers, a narrow bandpass diplexer, and a quadrature diplexer) are primarily used.
At present, the diplexer used in a dual-band (tri-mode) communication terminal is almost implemented by a chip.
In this case, as a frequency band used in the diplexer, a frequency band (hereinafter, referred to as cellular) of 824 to 894 MHz (AMPS) and a frequency band of 1850 to 1990 MHz (PCS) are used. The frequency band used in the diplexer serves to separate the duplexer into a cellular duplexer and a PCS duplexer and separate the duplexer into a duplexer for an intermediate-frequency mixer.
Herein, the duplexer is a primary component of a mobile communication terminal that serves to pass only a signal required in calling in connection with an antenna and remove a signal and noise which are unnecessary.
The diplexer in the related art serves to separate the frequencies of 824 to 894 MHz (AMPS) and a frequency band of 1850 to 1990 MHz (PCS) into the cellular duplexer and the PC duplexer in a high-frequency signal received through the antenna (Ant).
The diplexer is most configured by the chip and in terms of a characteristic thereof, insertion loss of a bandpass frequency is maximum 0.7 dB (0.4 dB typ), and isolation is minimum 15 dB.
For reference, the insertion loss (IL) as a result caused by inserting a transducer into a transmission system indicates a ratio of power P2 given to a predetermined place next to a transducer and power P1 given at the same place when the transducer is removed as a decibel (dB).
The isolation represents a power transfer amount from one antenna to another antenna and interantenna isolation indicates a ratio of reception power of another antenna to input power into one antenna as the decibel and a reception power ratio at the Rx side from Tx in RF is also one concept of the isolation.
The insertion loss of the PCS (0.4 dB Typ) and cellular (0.3 dB Typ) band frequencies is designed as approximately 0.7 dB Max (0.4 DB Typ).
Therefore, the diplexer implemented by one chip has a problem that since performance is implemented in the chip while an inputted frequency is separated into a dual band by an internal selection terminal, a coupling phenomenon and higher isolation which are caused therefrom can not obtained.
Since there is a high possibility that the chip will be damaged by heat generated from the chip is high, durability is weak.
In the related art, the diplexer uses a concentrated constant circuit and thus it is impossible to downsize the diplexer.